This application claims the priority of German Patent Application Ser. No. 199 47 806.6, filed Oct. 5, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to a chain drawing machine for continuous drawing of drawing stock, in particular of rod-shaped and tubular drawing stock. More particularly, the invention relates to a chain drawing machine with at least two drive chains and drawing members that have on one side a clamping shoe that can be pressed against the drawing stock, and on the other side a sliding surface which supports the drawing members via a rotating load-bearing idler rollers on a fixed roller guide associated with each driving chain.
Drawing stock that is made of metal and continuously drawn with a chain drawing machine is typically clamped between clamping shoes on a drawing path. The clamping shoes are moved in the drawing direction by continuously revolving drawing chains that are driven by chain wheels. To support the pressing forces without friction, the drive chains move on a plurality of load bearing idler rollers which also revolve continuously about fixed tracks or stationary roller guides. The drawing stock is clamped along the drawing path by clamping shoes disposed on at least two drive chains, with the clamping shoes being supported by corresponding roller guides and idler rollers disposed on the machine. When two drive chains are used, the roller guide are arranged in parallel on both sides of the drawing path. Other types of drawing machines can have several drive chains with clamping shoes that can optionally press symmetrically or asymmetrically against the drawing stock.
EP 0 548 723 B2 discloses a chain drawing machine of this type. The drawing members of the drive chains have on their backside, i.e., on the side facing away from the clamping shoes, a sliding surface thatxe2x80x94much like a roller bearingxe2x80x94runs over a moving chain that is guided on a stationary rigid roller guide consisting of the idler rollers. The clamping force is transferred directly through the idler rollers from the clamping shoes via the sliding surface to the roller guide. To achieve a stable machine construction and to compensate for the tilt of the guide rollers which tend to rotate out of alignment when an uneven force is applied, the guide rollers are arranged in the center. All sliding surfaces of the linearly arranged drawing members have a single sliding surface which is located opposite the rigid roller guide and extends over the same width as the idler rollers and the roller guide. The arrangement the contact surface in the center between the idler rollers and the sliding surface of the drawing members and the roller guide disposed on the machine, respectively, is intended to accurately introduce and/or distribute the force over the machine frame for minimizing wear of the idler rollers. The individual drawing members are connected with one another through bolts and include a complex arrangement of additional idler rollers and safety plates with matching geometrical dimensions.
It is thus an object of the present invention to provide an improved chain drawing machine, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved chain drawing machine that has a simpler construction and supports large clamping forces.
The invention relates to a chain drawing machine for continuous drawing of drawing stock with at least two drive chains associated with a common drawing path. Each of the drive chains has drawing members that are connected with one another and can be driven by means provided laterally on the drawing members. A clamping shoe that can be pressed against the drawing stock is disposed on one side of the drawing members, with a sliding surface disposed on the other side of the drawing members. The sliding surface supports the drawing members via a rotating load-bearing idler rollers on a fixed roller guide associated with each driving chain.
According to one aspect of the invention, the idler rollers interact with the sliding surface and/or the roller guide via a segmented contact surface and are guided at the height of the segmented contact surface only by guides that travel with the rollers. This arrangement obviates the need for a complex guide arrangement on the sliding surface and/or the roller guide, and hence significantly reduces the manufacturing costs. This arrangement also simplifies maintenance of the machine since a stationary guide or a guide that travels with the drawing members, is difficult to access.
According to another aspect of the invention, the roller guides for the drive chains can be separated into guide paths by a least one relief recess. Because the roller guides on which the idler rollers roll, are subject to manufacturing tolerances and are also not completely flat, the relief recess can provide a better fit between the idler rollers and the roller guide and thus increase the effective contact line or contact surface that supports the force.
Advantageously, the sliding plane of the drawing members can also be separated into sliding paths by providing at least one relief recess. It is particularly advantageous if the idler rollers are formed so as to be able to slightly yield resiliently relative to the entire width of all guide paths and sliding paths, for the purpose of adapting to the tolerances that may exist in the guide paths and sliding paths.
According to a first embodiment, the idler rollers extend across at least two guide paths, preferably each idler roller across all guide paths. Advantageously, the idler rollers have a circumferential taper associated with a respective relief recess for better adapting the idler rollers to the existing tolerances. Depending on the location of the relief recesses, the idler rollers are thereby intentionally weakened and/or their diameter is reduced in order to resiliently adapt and/or bend within certain limits across their width to compensate for tolerances in the guide paths and sliding surfaces.
According to another embodiment of the invention, the idler rollers are composed of two parallel guided sets of track rollers, wherein each guide path and/or sliding path is associated with one set of the track rollers. Mechanical guiding of the idler rollers and/or the sets of track rollers can be facilitated by connecting the sets of track rollers with one another through track roller cages or by implementing the sets of track rollers in form of chains.
The force can be distributed more evenly by placing the guide paths and the sliding paths opposite of each other uniformly and/or with an identical width. Moreover, at least one relief recess advantageously divides the roller guide and/or the sliding surface in the center. According to another advantageous embodiment of the invention, two guide paths and/or two sliding paths can be provided.
In addition, the drawing members may be connected with one another with a connecting bolt, wherein track rollers and/or tie elements are arranged on both sides of the drawing members on the connecting bolt. The force can be introduced and distributed more uniformly if the clamping shoes and the sliding surfaces are located on opposite, mutually parallel sides of the drawing members, wherein the clamping shoes and the sliding surfaces and/or sliding paths can be integrated with the drawing members to form a single piece.
According to another advantageous embodiment of the invention, the idler rollers are formed of at least two roller sections which are supported on a common axle. This arrangement is particularly cost-effective and can be implemented using standard building blocks while maintaining the same advantages as the aforedescribed embodiments. Preferably, a spacer, for example a sleeve disposed on the axle, can be placed between the roller sections.
In this embodiment, the idler rollers can advantageously be connected with one another in the form of a chain. Since the plates of the chain partially overlap, bending of the chain in the lateral direction is limited. This provides a simple outer guide for the idler rollers and/or the roller sections. The outer guide can absorb guide forces acting in the lateral direction.
Advantageously, the inner guide elements can absorb guide forces acting in the lateral direction. The inner guide elements travel with the rollers, are disposed at the same height as the contact surface separation, and do not come in lateral force-transmitting contact with stationary guide elements. Because the inner guide elements themselves can absorb the guide forces, inner components, such as stationary guide elements, become unnecessary. Eliminating the stationary guide elements frees up space and enables a more compact construction.
The laterally acting guide forces are to be understood as including those forces that include a force component acting in an imaginary plane that extends perpendicular to the guide plane.
The costs for design, manufacturing and subsequent maintenance also be advantageously reduced by eliminating the stationary guide elements.
Advantageously, the inner guide elements are arranged parallel to the sliding surface as well as between the sliding surface and the guide surface.
The inner guide elements are also present in the embodiment where the idler rollers consist, for example, of parallel guided sets of track rollers. This also obviates the need for stationary lateral components to guide the idler rollers.